Reductive oxidation of -nitrotoluene

Reductive oxidation of />-nitrotoluene to -aminobenzaldehyde, 31, 6 Reformatsky reaction, 37, 38 Reissert s compound, 38, 58 Reissert reaction, 38, 58 Replacement, benzenesulfonate groups by bromine atoms, 31, 82 bromine, by a thiol group, 30, 35 by fluorine, 36, 40 chlorine, by an amino group, 31,45 by a thiol group, 32, 101 by iodine, 30, 11 by methoxyl, 32, 79 by nitrile, 36, 50 in an imido-chloride group by an anilino group, 31, 48 chlorine and nitro by ethoxyl radicals, 32,68... 

The reduction of o-nitrophenyl acetic acids or esters leads to cyclization to oxindoles. Several routes to o-nitrophenylacetic acid derivatives arc available, including nitroarylation of carbanions with o-nitroaryl halides[2l,22] or trif-late[23] and acylation of o-nitrotoluenes with diethyl oxalate followed by oxidation of the resulting 3-(u-nitrophenyl)pyruvate[24 26]. 

Preparation of the prototype in this series, procaine (31). i.irts with the oxidation of p-nitrotoluene (27) to the corre-Hiding benzoic acid (28). This is then converted to the acid ll Inride (29) reaction of the halide with diethyl aminoethanol fiI lords the so-called basic ester (30). Reduction by any of a .fl ics of standard methods (e.g., iron and mineral acid, cata-Ivlic reduction) affords procaine (31). ... 

Reductive cyclization of o-nitrophenylacetic acids is a very general method of oxindole synthesis (see Section 3.06.2.1.1 for the application of this method to indoles in general). The main problem is efficient construction of the desired phenylacetic acid. One method involves base-catalyzed condensation of substituted nitrotoluenes with diethyl oxalate followed by oxidation of the 3-arylpyruvate (equation 200) (63CB253). Nucleophilic substitution of o-nitrophenyl trifluoromethanesulfonate esters, which are readily prepared from phenols, by dimethyl malonate provides another route (equation 201) (79TL2857). 

Small amounts of the N-oxide of 8 accompanied the formation of o,o -dinitrodiphenylethane by the reaction of o-nitrotoluene with potassium rert-butoxide [73AC(P)329 75MI4]. Formation of 8 and its N-oxide also resulted from the controlled-potential electrolysis of o-nitrobenzyl thiocyanate, a reaction proceeding by dimerization of the initially formed onitrobenzyl radicals followed by simultaneous or subsequent reductive coupling of the nitro groups. In strongly acidic medium, the reaction took a different course (85CCC33). 

Walther obtained the first direct dyes by self-condensation of 4-nitrotoluene-2-sulfonic acid. So-called Sun Yellow is a mixture of different components, depending on the concentration of sodium hydroxide, the temperature, and the duration of the reaction. Oxidation of the intermediate dye and subsequent reduction with iron and hydrochloric acid gives 4,4 diaminostilbene-2,2 -disulfonic acid, which is used for fluorescent whitening agents and azo dyes. The shades are mostly yellow to red. The structure of Direct Yellow 11, 40000 [65150-80-3] (13 is one of the main components) probably contains a mixture of stilbene, azo, and/or azoxy groups. 

The starting compound for all triazinylaminostilbenes is 4,4 -dinitrostilbene-2,2 -disulfonic acid [128-42-7], which is obtained by oxidizing 4-nitrotoluene-2-sulfonic acid with aqueous sodium hypochlorite in the presence of sodium hydroxide or, more recently, by atmospheric oxidation in an aqueous ammoniacal medium [39], The Bechamps reduction using iron filings etched with hydrochloric acid yields 4,4 -diaminostilbene-2,2 -disulfonic acid [81-11-8] (DAS). 

Reduction products of nitric acid, such as nitrogen and nitrogen oxides can also be formed as the result of oxidation processes. Niederer [148] found that N2 and NO were not formed in the nitration of nitro- to dinitrotoluene, while they were present in the nitration products of di- to tri-nitrotoluene. In addition to nitrogen and nitrogen oxide, carbon mono- and dioxide were formed in the last stage of nitration. Their amount and the CO to C02 ratio increased with temperature. 

Case-II. A similar situation wherein reduction of the nitro function precedes esterification. In this specific case the initial reaction involving the oxidation ofp-nitrotoluene gives rise to the formation of p-nitrobenzoic acid which on further reduction with tin and HCl yields p-aminobenzoic acid (PABA) and PABA being soluble in both acid and base is rather difficult to isolate. Moreover, PABA may be isolated only under precisely neutral conditions and that too after removal of the metal ions which eventually form complexes with it. 

Oxidative coupling of o-nitrotoluene gives 4,4 -dinitrodibenzyl which is reduced with hydrogen to the diamine. The diamine is pyrolyzed to give dihydrobenzazepine. This is reacted with N-(3-chloropropvl)-N-methylbenzamine to give N-benzyldesipramine. This is debenzylated by reductive cleavage and then reacted with HCI. 

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